210 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 10 



In respect to size relations some pertinent questions also arise. 

 Is it, for example, possible that a protoplasmic particle may be as 

 small, in small diameter, as a hemoglobin particle, remembering 

 that the former must carry the properties of surface and central 

 plasma and of nucleoplasm — indeed of all the characteristics of 



individual 



does not seem 



be affected by any consideration of the magnitude of the long 

 diameter of the individual. Such an individual could not 

 presumably penetrate cell walls, and its rapid spread through 

 the tissues would be dependent upon bridging protoplasmic 

 fibrils between the cells. 



If one is compelled to admit the existence of an organism of 

 the size relations above referred to, it would seem necessary with 

 the data at hand to conceive of it as a flagellum-like creature 

 with perhaps a temporary hook-up of molecules or colloidal 

 particles, conceivably with no true bordering membrane and no 

 restricted endometabolism. The supposition that the organism 

 might be of an extremely fluid nature would perhaps be equally 

 unsatisfying. 



Taking into consideration all the facts, we cannot avoid the 

 impression, tentatively, that the causal agency in mosaic disease 

 may be, in any particular case, a sometime product of the host 

 cell; not a simple product such as an enzyme, but a particle of 

 chromatin or of some structure with a definite heredity, a gene 

 perhaps, that has, so to speak, revolted from the shackles of 

 coordination, and being endowed with a capacity to reproduce 

 itself, continues to produce disturbance and "stimulation" in 

 its path, but its path is only the living cell. 



BIBLIOGRAPHY 



Allard, H. A. ('16). The mosaic disease of tomatoes and petunias. Phytopath. 

 6: 328-335. /. 1-2. 1916. 



— , ('16a). Some properties of the virus of the mosaic diseases of tobacco. 



Jour. Agr. Res. 6:649-674. pi. 91. 1916. 



, ('16b). A specific mosaic disease in Nicotiana viscosum distinct from 



the mosaic disease of tobacco. Ibid. 7: 481-486. pi. 85-86. 1916. 



, ('18). Effects of various salts, acids, germicides, etc., upon the infec- 



tivity of the virus causing the mosaic disease of tobacco. Ibid. 13: 619-637. 



1918. 



